For the \(\vec{\phi }\)  Lagrangian I take [1]}
\({\cal L}_\phi = \frac{( \partial _0 \vec{\phi })^2}{2} + \frac{( \partial _i^2 \vec{\phi })^2}{2 M^2}+ \frac{Z( \partial _i \vec{\phi })^2}{2}+ \frac{m_0^2\vec{\phi }^{\, 2}}{2}+ \frac{\lambda (\vec{\phi }^{\, 2})^2}{4} \; ,\) 
